The standard advice to eat more vegetables is rarely questioned. I consume a great variety but some traditional cultures did not and the ones that did, prepared them in ways to help them absorb the nutrients and increase their digestibility. I believe the all raw veggie diet is not the best advice. Read Myths and Truths of a Vegetarian Diet.
It’s best to consume veggies that are grown in healthy organic soil. Try to buy in season and local. When vegetables are allowed to ripen on the plant, their nutrient content is much higher. It’s also beneficial for the environment not to burn fossil fuels to ship our food great distances.
Some veggies are best eaten cooked. For example, cabbage, broccoli, Brussels sprouts and kale contain chemicals that block the production of thyroid hormone. These are best eaten after they have been lightly steamed, fermented or stir-fried in butter, ghee or lard. Beet greens, spinach and chard contain oxalic acid that blocks calcium and iron absorption. Raw potatoes contain substances that disrupt the proper function of red blood cells. Cooking or fermenting destroys or neutralizes these harmful substances.